Field of the Invention
The present invention relates to a method of evaluating a resin, including evaluating a deterioration degree of the resin.
Description of the Related Art
Acetic acid is a basic chemical that finds use in a wide variety of applications such as raw materials for polyvinyl acetate, acetylcellulose, and acetates, and a solvent for a terephthalic acid-producing plant. A methanol carbonylation method involving carbonylating methanol with carbon monoxide in the presence of a catalyst to produce acetic acid has been known as a method of producing acetic acid.
Available as the methanol carbonylation method is a method involving using, as a catalyst, a solid catalyst obtained by causing a resin as a carrier to carry a precious metal complex on itself such as a catalyst obtained by causing a resin, which has a side chain having a nitrogen-containing aromatic ring group such as a pyridine group and a crosslinking portion, to carry a rhodium complex (see Japanese Patent Application Laid-Open No. H6-315637 and Japanese Patent Application Laid-Open No. 2012-81440).
The methanol carbonylation reaction is performed under heat or pressure (e.g., a condition of a temperature of from 130° C. to 190° C. or a pressure of from 3 to 5 MPa), and hence the resin as a carrier decomposes to deteriorate. As the decomposition progresses, there arises a problem in that the particulate carrier resin is reduced in its average size to clog, for example, a screen to be placed at an outlet of a reactor for the carbonylation reaction, a problem in that the carrier resin is liable to powder owing to a reduction in its crosslinking degree, or a problem in that an amount of the nitrogen-containing aromatic ring group such as a pyridine group on the carrier resin reduces, and hence an ability of the resin to immobilize the precious metal complex made of rhodium or the like reduces, and by extension, an ability of the catalyst reduces.
Therefore, the deteriorated carrier resin needs to be exchanged before any such problem arises. In order that a timing at which the carrier resin is exchanged may be determined, a method of quantitatively evaluating a deterioration degree of the carrier resin with high accuracy and ease has been desired.
It should be noted that such evaluation for the deterioration degree of the resin has been desired not only in the catalyst to be used in the methanol carbonylation reaction but also similarly in any other resin.